HARRISBURG, Pa. (CBS) – State and federal agencies say they are looking into allegations by an environmental group that natural gas drilling on state land in Pennsylvania may be in violation of terms that were stipulated when the state accepted federal funds to purchase some of that land.

Since 1965, Pennsylvania has received more than $160 million from the federal government to acquire land that, according to the funding, must be used for public purposes in perpetuity.

Now, the Sierra Club says all leasing and drilling permitting for state parks and forest land should be halted until compliance with the federal law can be determined.

National Park Service spokesman Phil Sheridan says only the land purchased with federal money would be in question.

“Not all parkland would have been necessarily acquired with Land and Water Conservation [Act] money,” he says. “For example, if you think of a park as a big circle, we may only have a small piece of the pie that was funded that way. That’s the area that falls within the requirements of the law.”

A spokeswoman for the Pennsylvania Department of Conservation and Natural Resources says there is no deep-well natural gas drilling going on state parks and adds that the agency is optimistic that the vetting process for leases would have turned up any deed restrictions in state forest land.